* Forums are disowned on user account deletion (their owner_id=0)
* A forum without an owner shows a notice at the bottom with a link to petition
to adopt the forum. It goes to the Contact form with a special subject.
* Note: there is no easy way to re-assign ownership yet other than a direct
database query.
* Code cleanup
* Alphabetize the DB.AutoMigrate tables.
* Delete more things on user deletion: forum_memberships, admin_group_users
* Vacuum worker to clean up orphaned polls after the threads are removed
* Add the PollVotes table and associated logic.
* Multiple choice polls supported.
* Expiring and non-expiring polls.
* Icons and badges on the forum pages to show posts with polls
* Bugfix: non-explicit users getting SQL errors on Newest Posts page.
Got initial Poll table and UI started:
* Polls can be attached to any NEW forum post (can't edit poll details
after creation)
* Max 100 options (theoretically unlimited), expiration time.
* UI: shows radio button list on posts having a poll, no submit handler
yet created.
